用C++程序求1+1+1/2！+1/3！+．．．+1/n!

Question

还要求n=5和n=10的结果，保留十位小数！

Answer 1

#include <stdio.h>

int fun (int f) //计算f的阶乘
{
if (f<=1)
return 1;
else
return f*fun(f-1);
}

void main()
{
double n = 0;
double sum = 1;

cin >> n;

for (double i=1; i<=n; i++)
{
sum += 1/fun(i);
}

printf ("%.10f\n", sum);
}

Answer 2

#include <iostream>
using namespace std;

int main()
{
int n = 0;
double sum = 1;
long int Factorial_n =1;

cin>>n;

for (int i=1; i<=n; i++)
{
Factorial_n*=i;
sum += (double)1/Factorial_n;
}
不懂

printf ("%.10f\n", sum);
return 0;

}

Answer 3

#include <iostream>
using namespace std;

int main()
{
int n = 0;
double sum = 1;
long int Factorial_n =1;

cin>>n;

for (int i=1; i<=n; i++)
{
Factorial_n*=i;
sum += (double)1/Factorial_n;
}

printf ("%.10f\n", sum);
return 0;

}